Top Russian boxer Aleksandr Povetkin has failed a drug test ahead of his world heavyweight title fight with reigning champion Deontay Wilder, Povetkin's promoter said.
Povetkin tested positive for meldonium, the same substance found in tennis star Maria Sharapova's sample at the Australian Open, promoter Andrei Ryabinsky said on May 13.
"We're in contact with the [World Boxing Council]. They'll take the decision on whether the fight will happen or not," Ryabinsky said.
The bout is scheduled for May 21 in Moscow.
Ryabinsky admitted Povetkin took meldonium last year, but said he stopped before it was banned on January 1, and only "leftover traces of meldonium at a very low concentration" were found in a blood sample given by Povetkin last month.
Athletes in several sports have avoided suspensions for meldonium positives under new World Anti-Doping Agency guidance issued last month, if the concentration of the banned heart drug is low enough to indicate they did not take it after January 1.
Povetkin is an experienced Russian heavyweight with 30 wins and only a single loss. Unbeaten American Wilder, who has said he is eager to fight in Russia, has won 36 fights, all by way of knockout.